Ethylene Recovery From Off-Gas

Abstract

A method for the recovery of ethylene from an off-gas is provided. This method includes providing an ethylene containing feed gas stream, introducing the ethylene containing gas stream into a first cryogenic separation device, thereby producing a first condensed stream and a first ethylene poor stream, and introducing the ethylene poor stream into a first feed compressor, thereby producing a pressurized first ethylene poor stream. This is repeated three times, resulting in a pressurized third ethylene poor stream, which is introduced into a pressure swing adsorber, thereby producing a high purity hydrogen stream and a PSA tail gas stream. The PSA tail gas stream is into a PSA tail gas compressor, thereby producing a pressurized PSA tail gas stream, which is then combined with an ethylene containing gas stream to produce the ethylene containing feed gas stream. The first condensed stream, the second condensed stream and the third condensed stream are combined to produce a combined condensed stream, which is introduced into an ethylene separation column thereby producing an ethylene rich stream and a methane rich stream. The methane rich stream is introduced into a methane compressor thereby producing a methane fuel stream.

1 : A method for the recovery of ethylene from an off-gas, comprising;
 a) providing an ethylene containing feed gas stream,   b) introducing the ethylene containing feed gas stream into a feed compressor, thereby producing a pressurized ethylene containing feed stream,   c) introducing said pressurized ethylene containing gas feed stream into a cryogenic separation device, thereby producing an ethylene rich stream, a high pressure methane rich stream, a low pressure methane rich stream, and an ethylene poor stream,   d) introducing said ethylene poor stream into a pressure swing adsorber, thereby producing a high purity hydrogen stream and a PSA tail gas stream,   e) introducing said PSA tail gas stream into a PSA tail gas compressor, thereby producing a pressurized PSA tail gas stream, which is then combined with an ethylene containing gas stream to produce said ethylene containing feed gas stream,   f) introducing said low pressure methane rich stream to a methane compressor thereby producing a methane fuel stream.   
     
     
         2 : The method of  claim 1 , wherein said ethylene containing gas stream has less than 10% ethylene. 
     
     
         3 : The method of  claim 2 , wherein said ethylene containing gas stream has less than 5% ethylene 
     
     
         4 : The method of  claim 2 , wherein said ethylene containing gas stream has less than 60% methane. 
     
     
         5 : The method of  claim 2 , wherein said ethylene containing gas stream has less than 50% hydrogen. 
     
     
         6 : The method of  claim 1 , wherein said ethylene containing gas stream has a composition of about 40% hydrogen, about 58% methane, and about 2% ethylene. 
     
     
         7 : The method of  claim 1 , wherein said high purity hydrogen stream has a pressure of about 300 psig. 
     
     
         8 : The method of  claim 1 , wherein said methane fuel stream has a pressure of about 75 psig. 
     
     
         9 : A method for the recovery of ethylene from an off-gas, comprising;
 a) providing an ethylene containing feed gas stream   b) introducing said ethylene containing gas stream into a first cryogenic separation device, thereby producing a first condensed stream and a first ethylene poor stream,   c) introducing said ethylene poor stream into a first feed compressor, thereby producing a pressurized first ethylene poor stream,   d) introducing said pressurized first ethylene poor stream into a second cryogenic separation device, thereby producing a second condensed stream and a second ethylene poor stream,   e) introducing said second ethylene poor stream into a second feed compressor, thereby producing a pressurized second ethylene poor stream,   f) introducing said pressurized second ethylene poor stream into a third cryogenic separation device, thereby producing a third condensed stream and a third ethylene poor stream,   g) introducing said third ethylene poor stream into a third feed compressor, thereby producing a pressurized third ethylene poor stream,   h) introducing said pressurized third ethylene poor stream into a pressure swing adsorber, thereby producing a high purity hydrogen stream ( 120 ) and a PSA tail gas stream,   i) introducing said PSA tail gas stream into a PSA tail gas compressor, thereby producing a pressurized PSA tail gas stream, which is then combined with an ethylene containing gas stream to produce said ethylene containing feed gas stream,   j) combining said first condensed stream, said second condensed stream and said third condensed stream to produce a combined condensed stream,   k) introducing said combined condensed stream into an ethylene separation column thereby producing an ethylene rich stream and a methane rich stream, and   l) introducing said methane rich stream to a methane compressor thereby producing a methane fuel stream.   
     
     
         10 : The method of  claim 9 , wherein said ethylene containing gas stream ( 101 ) has less than 10% ethylene. 
     
     
         11 : The method of  claim 10 , wherein said ethylene containing gas stream has less than 5% ethylene 
     
     
         12 : The method of  claim 10 , wherein said ethylene containing gas stream has less than 60% methane. 
     
     
         13 : The method of  claim 10 , wherein said ethylene containing gas stream has less than 50% hydrogen. 
     
     
         14 : The method of  claim 9 , wherein said ethylene containing gas stream has a composition of about 40% hydrogen, about 58% methane, and about 2% ethylene. 
     
     
         15 : The method of  claim 9 , wherein said high purity hydrogen stream has a pressure of about 300 psig. 
     
     
         16 : The method of  claim 9 , wherein said methane fuel stream has a pressure of about 75 psig.